Mutations in the human kinesin gene KIF1A cause a variety of neurological defects. This syndrome has remained poorly defined because of the rarity of the condition. This proposal brings together the very different, but highly complementary expertise of Dr. Wendy Chung at Columbia University Medical School, a specialist in human genetic disease; Dr. Richard Vallee, also at Columbia, an expert in the role of Kif1a in neuronal development and physiology; and Dr. Arne Gennerich, at Albert Einstein College of Medicine, an expert in motor protein biophysics. Dr. Chung's lab has developed clinical and computational methods to compile information from patients locally and worldwide on the range, severity, and variety of symptoms associated with this condition, which her lab has termed KAND KIF1A Associated Neurological Disorders. This is a heterogeneous group of severe neurodegenerative conditions, including spastic paraplegia, peripheral neuropathy, optic nerve atrophy, cerebral and cerebellar atrophy, cognitive impairment, and seizures. The condition available. The over-all goals of this project are to obtain sufficient clinical information to understand the full-range of KAND symptoms; to determine how mutations at diverse sites within the Kif1a motor domain impact clinical outcome; to understand the cellular and developmental causes of the syndrome; and to identify small molecule reagents to treat it. Aim 1 will be to define the natural history of KAND based on a rapidly increasing patient database and correlate clinical severity and rate of progression with KIF1A genotype. Aim 2 will be to use advanced single molecule biophysical and in vivo axonal transport approaches to determine the molecular and cellular consequences of the Kif1a mutations. Aim3 will be to use Kif1a mutant mice to determine the longitudinal and cross-sectional effects of the condition in a model organism, and to test more completely the role of BDNF in KAND and the value of small molecule BDNF mimetics as KAND therapeutic agents. These studies are of great importance for a number of reasons. They will dramatically extend our capability to identify and characterize rare diseases. They will provide detailed insight into the molecular basis of a motor protein-associated disease. They will provide extensive new information on the progression of the disease and the relationship of mutation site to prognosis. And, they will take advantage of our new molecular and physiological insights into gene function to develop targeted therapies. can be fatal, and there is at present no treatment